Who Will Win the Race:
Light Bulbs or Fluorescent Tubes?
The big question is: Which light source provides the higher light output per watt of electricity? Many believe that flourescent lamps have a 5 times higher light output per watt. That is true with standard light bulbs. But it is not true for modern state of the art light bulbs.
An archaic technology: Electric current heats a thin wire so much that it glows yellow and white. Refined during a period of roughly 150 years, light bulbs deliver at least 1000 hours of good light. However, about 98 percent of the electrical energy is released as heat.
Halogen lamps - hot, white and more durable
A dramatic development of the conventional incandescent lamp are halogen lamps operated at higher temperatures. Thus, the light is closer to natural light and the energy conversion is more efficient - after all, roughtly 3-4 percent of the electrical energy is converted into light. 40 percent more than the traditional bulb.
And the life increases - despite the higher operating temperature of the wire. Halogen gas in the glass of the lamp provide a repair mechanism. The heat extracts metal atoms from the filament but by the halogen admixtures these atoms were attached to the filament.
Halogen lamps with infrared coating
The main drawback of light bulbs is that the major part of the emitted electromagnetic radiation is (invisible) infrared radiation. Reflecting back the infrared radiation would heat the filament at reduced electric power input.
Modern heat-resistant infrared reflecting coatings are the solution. Halogen lamps which are equipped with such a coating of the glass bulb, have efficiencies of 5-7 percent and thus have twice the efficiency of traditional light bulbs! And for free: The life span is increased from 1000 to 4000 - 5000 hours!
Compared with the energy saving lamps ...
A state of the art energy-saving lamp (flourescent lamp) has at least twice the efficiency again. However, it has different drawbacks: Fluorescent lamps
- require a start-up time of at least a few minutes to reach their design intensity,
- have no continuous (sun-like) spectrum,
- show brightness degradation during their lifetime,
- incorporate mercury and other heavy metals (e.g. thorium) and
- are no point source, disabling flourescent tubes for spotlight applications.
Modern halogen lamps with infrared coating reach - perfect for light properties - after all, only the energy efficiency class B instead of A for energy-saving lamps.
But let us wait some 2 or 3 years, and the light bulb might match or surpass flourescent and LED lamps in the discipline of energy efficiency. In all other disciplines the halogen lamp with IRC is equal or much better than its replacement candidates.